Anxiety in cats..?

I cant remember if I posted about this once before but I just moved about five months ago and all the critters have been adjusting well. Kinky likes to stand up on the screen door and look outside. Well I saw him doing this a while back and however long later he started howling and he was panting and drooling. So I rushed him upstairs to my bedroom and wiped him off and cuddled him and he calmed down. Today the same thing happened. He was looking out the door, a little while later he started howling and was panting and drooling. I brought him upstairs, closed the curtains and cuddled him until he started to purr. The other cats are sniffing him so he must smell a little odd. But now he's pretty much back to normal. I locked him in the bedroom with the rest of the kitties so he would feel secure. Has anyone ever experienced this before? Its so weird.

Not something I`ve experienced but is it possible he can see something he doesn`t like ( Cat / dog ) from the door or maybe some birds real close that`s getting him excited?